Purchased an LS1 off of a guy and he gave me two sets of pistons. Both sets have very few markings

Set 1 Only markings I could see is "LS28H12ID" laser engraved

Pistons 1

Pistons 1

Pistons 1

Set 2. All marked "418" in marker which I assume is the weight. Also cast with "T071" and "99L4"

Pistons 2

 

I'd be measuring the diameter on them, 418 might be the size of the Engine that can be built if they are from someone's extra parts laying around they were getting together. Anything is possible.

Laser etched might be a part number, Google it.

This is more for the Gen III Internal Engine section. You have Pistons that go external of the Engine you have bigger problems than figuring out what they are..

 

I'd measure the first one to be sure.
As for the second one: 99L4 is a Mahle LS1 piston, part number 027020.

 

418 could be the weight of the pistons too but seems fairly light